The primary clinical goal of the research is to test if chronic intrathecal balclofen is a safe and effective means of treating spasticity due to cerebral trauma and cerebral palsy. As in our prior studies, balanced randomized double-blind crossover trials on and off balclofen will be performed. Tests appropriate to each patient's disability will be used to measure muscle tone, reflexes, spasms and voluntary motor control. Activities of daily living on and off baclofen will also bes assessed. If improvement is found, baclofen will be continued and long-term monitoring will be carried out to determine the frequency of drug and device problems. Previously treated multiple sclerosis and spinal cord injury patients will continue to be followed, since they are the original group of patients treated with baclofen and are therefore an important resource of judging long-term efficacy. A secondary goal will be to study the effects of intrathecal baclofen on spinal reflexes and voluntary control. the Motor Control Laboratory testing will quantify changes in monosynaptic and polysynaptic reflexes and patterns of voluntary muscle activation on and off baclofen. This project has broader importance than just a unique treatment for spasticity. It could demonstrate the efficacy of long-term direct perfusion of neurotransmitters and their agonists and antagonists into the central nervous system. This novel approach, if successful, should encourage further experimental drug therapies for a wide range of neurological diseases.